1. Field of the Invention
The present invention relates generally to a pointing input device, and more particularly, to a pointing input device having a magnetic field shielding layer which transmits Earth's magnetic field sensed by a geo-magnetic sensor.
2. Description of the Related Art
With the rapid development of markets related to smart phones or touch screens, research has been actively conducted on these devices. A touch screen is widely used as an input device of a mobile terminal and generally includes a transparent electrode. The touch screen of a capacitive type, which measures a change in electrostatic capacity occurring due to a touch is commonly used, however, in the capacitive-type touch screen, a user must provide a predetermined pressure or displacement by contacting the touch screen, and cannot perform an input operation by using a pen.
To overcome these disadvantages, a touch screen using electromagnetic waves has recently become popular. A pointing input device using this scheme can be classified into various types, an example of which is an Electro-Magnetic Resonance (EMR) type.
However, an electronic device such as a mobile terminal, etc., often includes a tool for mounting a pointing input device, a battery, various circuit units, etc., which may block or disturb a magnetic field. As a result, the performance of the pointing input device is negatively affected. To prevent such a negative influence, a magnetic field shielding layer is used.
A mobile terminal employs various additional functions to improve convenience and entertainment of a user. For example, a screen changes according to the amount of movement of the mobile terminal. To sense the movement, the mobile terminal is equipped with a geo-magnetic sensor. However, if the geo-magnetic sensor is provided in the pointing input device, the operation of the geo-magnetic sensor may be affected by the magnetic field shielding layer.
In addition, in a mobile terminal are mounted parts having strong magnets, such as a speaker, a camera, etc., as well as the geo-magnetic sensor. Such magnetic parts generate a strong low-frequency magnetic field, and thus there is a need for a magnetic field shielding layer.
The magnetic field shielding layer prevents an eddy current from being induced, allowing accurate tracking of a position of an electromagnetic pen. However, if the geo-magnetic sensor is disposed near the magnetic field shielding layer, a low-frequency magnetic field such as the Earth's magnetic field is blocked or distorted by the magnetic field shielding layer, making it difficult to perform an accurate geo-magnetic sensing operation.
Therefore, there is a need for a magnetic field shielding layer which prevents attenuation of the magnetic field by blocking the magnetic field generated by the tool, the battery, the various circuits, etc., disposed under the magnetic field shielding layer, while transmitting Earth's magnetic field sensed by the geo-magnetic sensor and not affecting the operation of the geo-magnetic sensor. Moreover, when a pointing input device such as the mobile terminal includes magnetic parts, a magnetic field shielding layer is required which effectively blocks a strong low-frequency magnetic field signal, and at the same time, transmits a low-frequency magnetic field guaranteeing an operation of the geo-magnetic sensor.